Field of the Disclosure
The present disclosure relates to agricultural and earthmoving implements, generally relating to implements for tilling, plowing and seeding, equipped with hydraulic control systems, and more specifically, to structure for providing constant pressure relief protection from excessive or sudden hydraulic pressure increases within a system designed to exert a constant downward force on the ground.
Description of the Related Art
This disclosure pertains to agricultural and earth moving implements operated hydraulically. A hydraulic system enables an implement to be raised and lowered. While in a lowered position, the hydraulic system maintains a constant downward pressure between an implement, such as agricultural components, and the ground surface, as described, for example, in U.S. Pat. No. 5,065,681.
However, due to many possible factors including, for example, slopes and topographical variations of the ground surface, and changes in vehicle position relative to the ground, the hydraulic pressure can vary significantly during operation. This necessitates the hydraulic system adapt the fluid pressure and displacement of a hydraulic cylinder so that the pressure between the agricultural components and the ground can be maintained as the agricultural implement traverses uneven terrain, or encounters obstacles of any kind.
Under certain conditions the hydraulic fluid pressure can rapidly increase due to operator error, an abrupt change in terrain or impact with an obstacle, such as a rock or tree stump. If hydraulic fluid stops flowing within the circuit for any reason, the hydraulic circuit is then effectively locked and, if hydraulic pressure increases rapidly, there is no means to quickly evacuate the hydraulic fluid inside the system to prevent buildup of additional pressure.
One scenario where this can occur, for example, is when the agricultural components are set on or close to the ground and the operator does not open the Selective Control Valve (SCV) and then proceeds to drive the agricultural implement over an obstacle. The impact of the agricultural components abruptly striking the ground or obstacle can cause pressure in the hydraulic cylinder to quickly increase. With the SCV closed, oil cannot escape. If the peak pressure reached inside the implement's hydraulic circuit is sufficiently high, damage to the mechanical structure or hydraulic system can occur. The increased operating speed of modern agricultural implements requires hydraulic systems to respond quickly to changes in hydraulic system pressure to prevent damage to system components.